Process for the preparation of supported, non-pyrophoric, skeleton catalysts of polar surface

ABSTRACT

According to the invented process an alloy powder of catalytically active metal(s) and alkali-soluble metal(s) is suspended in a solution having a weight 3-10 times of that of the alloy and containing 0.5-4 wt % of an alkali hydroxide, where the amount of alkali hydroxide in the solution used is 5-30% of the weight of the alloy, or the alloy powder is suspended in water and a solution containing amount of alkali hydroxide is dropped to it, the suspension is heated at 90-100° C. until the intensive hydrogen development stops, then a solution containing 10-40 wt % alkali hydroxide is added to the suspension in such amount that the content of the alkali hydroxide relative to the weight of the starting alloy is 10-60 wt %, the suspension is stirred at 30-100° C. for further 3-60 minutes, and the solid phase is separated and washed to neutral.

The subject of the invention is the preparation of supported,non-pyrophoric, skeleton catalysts containing catalytically activemetal(s), preferably nickel, cobalt, chromium, copper, manganese, iron,palladium and/or platinum.

The skeleton-metal (or Raney-metal) catalysts are made of alloys thatcontain catalytically active metal or metals (e.g.: Ni, Co, Fe, Cu, Pd,etc.) and easily dissolvable, catalytically inactive component orcomponents (e.g.: Al, Si, Mg, Zn). In the alloy the active metal is"dissolved", i.e. it is finely dispersed. The inactive component isremoved from the alloy using a solvent (generally aqueous alkalisolution) not attacking the active metal. The active metal is left overas a catalyst in the form of fine particles. The activity of thecatalysts made this way is greater than the one produced from theappropriate metal oxide with reduction. Their importance and wide-spreadapplication are explained by the exceptionally high activity.

Skeleton catalysts were first patented by Raney (Raney, M.: U.S. Pat.Nos.: 1,563,787 (1925); 1,628,191 (1927); 1,915,473 (1933)).

From the alloy normally containing about 50% active metal and about 50%inactive component, the latter component is generally dissolved in twosteps (Schroter, R.: Neuere Methoden der praparativen organischenChemie, Verlag Chemie GmbH, Berlin, 1943, p. 78; Beregi, L.: MagyarKemikusok Lapja 9, 234 (1954) Csros, Z., Petro, J. and Voros, J.: MTAKm. Tud. Oszt. Kozl. 9, 433 (1957)): The steps are the following:

(1) initial alkaline wash, and

(2) final alkaline wash.

The initial alkaline wash is generally carried out by adding the alloyto a 15-25 wt % alkali solution which amounts to four times the weightof the alloy (it is normally added slowly because of the intensivehydrogen development and the exothermic reaction). Then the mixture isheated until the hydrogen development is finished. The alloy to alkalisolution--and the alloy to alkali hydroxide ratios, which arecharacteristic on this step, are given in weight-parts of the alloy, onthe basis of the data of related references (Katalysatoren nach Raney,Merkblatt, Degussa (1967) p. 7):

    ______________________________________                                        NaOH solution  Solution/alloy                                                                              Alloy/NaOH                                       wt %           wt. ratio     wt. ratio                                        ______________________________________                                        13             12            2                                                20             4-5           0.8-1.0                                          25             4             1.0                                              ______________________________________                                    

When the initial alkaline wash is finished, the solution is separated bydecantation and generally the suspension left is heated again with afresh alkali solution using the same amount as for the initial alkalinewash, in order to complete the dissolution process.

The above process steps are in accordance with the present generalpractice. In modem industrial and commercial reviews generally aboveprocess descriptions can be found (Die Wirksamkeit speziellerRaney-Nickel-Katalysatoren mit definierte Eigenschaften fur chemischeReaktionen. Informationen, DODUCO (1967).2.0).

The catalytic features of the catalyst made from a given alloy aredecisively influenced by the conditions of the alkaline wash or washesdescribed above. For example when dissolving a nickel-aluminium alloythe crystal system of the alloy containing the aluminium is rearranged.The way and extent of rearrangement changes with the time andtemperature of the operation and with the amount of alkali (Wagner, H.,Schwab, G. and Stolger, I.: Z. phys. Chem. B. 27, 439 (1934)). As aconsequence the method of dissolving the alloy is decisive on thecatalytic features of the product.

According to the U.S. Pat. No. 3,809,658, the starting alloy powder isdecomposed first, in a wet solid phase using water and a small amount ofalkali hydroxide, and then the process is finished with a followingintensive dissolving treatment using concentrated alkali hydroxidesolution at a temperature around 100° C.

As it is obvious from the related literature dozens of processvariations have been tried in this field. All of them, withno-exception, are characterised by a first step wherein 20-30 wt %aqueous alkaline was used in an amount which was at least three-fourtimes, but often 8-12 times the weight of the alloy. The objective ofthe invention is to provide a process for the preparation of asupported, non-pyrophoric skeleton catalyst, which process is fast,environmentally friendly, economical and characterised by simpletechnical feasibility.

It was found that the objective can be achieved, if the skeletoncatalysts containing nickel, cobalt, chromium, copper, manganese, iron,palladium and/or platinum are produced from an alloy of catalyticallyactive metal(s) and alkali-soluble metal(s), powdered to granulessmaller than 200 μ, by treating the alloy with an alkali hydroxide sothat the powder is suspended in a solution having a weight 3-4 times ofthat of the alloy and containing 0.5-4 wt % of an alkali hydroxide,where the amount of alkali hydroxide in the solution used is 5-30% ofthe weight of the alloy, and the solution optionally contains ammoniumchloride, or sodium chloride, or potassium chloride, and/or lithiumchloride in an amount of 0.5-5% of the weight of the alloy, and thesuspension is heated at 90-100° C. until the intensive hydrogendevelopment stops. Alternatively the alloy powder is partly suspended inwater and said amount of alkali hydroxide is added to the stirredsuspension. Then a solution containing 10-40 wt % alkali hydroxide isadded to the suspension in such amount that the content of the alkalihydroxide relative to the weight of the starting alloy is 10-60 wt %,the suspension is stirred at 30-100° C. for further 3-60 minutes, andthen the solid phase containing the active metal(s) and theoxide-hydroxide formed from the alkali-soluble metal(s) is separated andwashed to be neutral.

The process according to the invention is based on the recognition thatif the disintegration of the alloy is done with a diluted, aqueousalkaline wash in which the amount of alkali is not enough to dissolvethe alkali-soluble metal completely, then a significant part of thismetal forms with water oxide/hydroxide not dissolving in the solution,therefore, as a support it stabilizes the active metal and increases itsdispersion. The active metal content of the skeleton catalysts preparedaccording to the present invention is generally between 20 and 50 wt %(in contrast with the 93-98% metal content of the known catalysts). Theskeleton catalysts prepared according to the invention show thefollowing significant differences in comparison with the conventionalpreparations: they are non-pyrophoric, those that contain nickel are notmagnetic, their relative density is significantly smaller (around 1g/cm³), their specific catalytic activity is higher and because of theiraluminium oxide/hydroxide content, their surface is polar. All thesecharacteristic features can be partly explained by the structuraldifferences. For example the X-ray examination of the nickel skeletoncatalyst made according to the invention showed that, unlike theconventional catalysts, in which the metal crystallites are generallybulky (about 200-nm size) and uniform, crystallites are present in twosizes, one of them is about one order of magnitude smaller than that inthe conventional catalysts, about 20 nm, and the other one is X-rayamorphous, having a crystallite size of about 2-3 nm. This explains thatthe catalyst is not ferromagnetic like the known preparations. The X-rayexaminations also showed that in the process of the catalyst preparationgypsite (Hidrargillit, Al₂ O₃ 3H₂ O) is developed from a part of thealuminium component and this acts as catalyst support. The BET surfacemeasurements and the computer analysis of the adsorption data showedthat most of the surface is present within meso-pores which are"ink-bottle" shaped, whereas the pores of the conventionally madecatalysts are characterised by voids between the flat surfaces of themetal crystallites. The presence of the aluminium oxide/hydroxide as acarrier, and that the well dispersed nickel particles are embedded causethat the catalysts made according to the present invention arenon-pyrophoric and their relative density is smaller than that of theknown ones, furthermore, when dried, their specific surface area isabout 40 times as much as the surface area of the conventional catalysts(about 40 m² /g, while for the conventional catalysts about 1 m² /g).

According to the invention it is advantageous to add all the granularpowder of the starting alloy at the same time to the diluted alkalisolution, in which the amount of the alkali hydroxide is only 5-30 wt %of the weight of the alloy, which ensures the disintegration of most ofthe alloy, but the alkali amount is not enough to bring all thealuminium into the solution as aluminate. The amount of the used alkalihydroxide depends on the granule size of the powdered alloy; the largerthe particles are (e.g. around 100-200 μ), the closer is to 30 wt %, andvica versa. It is also possible to proceed so that the alloy powder issuspended in water and the alkali is added dropwise into the solutionwhile stirring. If a small amount of ammonium chloride, or sodiumchloride, potassium-chloride or lithium-chloride is dissolved in thediluted alkali, it makes the disintegration of the alloy morecontrollable and simpler, it reduces the intensity of foaming caused bythe hydrogen development and it also increases the catalytic activity.Close to the end of the disintegration process of the alloy anothersolution is added containing 10-60 wt % alkali hydroxide relative to theweight of the alloy as a more concentrated, 10-40 wt % solution. Itsrole is to make the disintegration complete and to remove the smallamount of aluminium hydroxide that might get precipitated on the surfaceof the formed metal crystallites. The amount of the used alkalihydroxide within the given limits depends on the granule size of thealloys as described above.

The starting alloy which can be used consists of elements that dissolvein alkali, preferably of aluminium, silicon, or aluminium-silicon, andof active metal present in an amount of 30-60 wt %, preferably 50 wt %.Preferably the granule size of the alloy powder is smaller than 200 μm.Preferably sodium hydroxide or potassium-hydroxide can be used as alkalihydroxide.

The reaction is started at room temperature than the temperature isincreased. At a temperature of about 50° C. the phase of the alloyrichest in aluminium is dissolved during intensive hydrogen evolution,and then at 90-100° C. the main mass is dissolved. The maximum foamvolume is 1.5-2 times the volume of the solution. In the case of 50 galloy the dissolution is generally completed in 20-30 minutes and theprocess time of catalyst preparation is generally between 40 and 90minutes.

At the end of the process the simplest way of separating the catalystand the reaction mixture is decanting. The solid residue is washed withwater to be neutral, filled in a graduated cylinder and after it settlesdown, the end volume is measured. Then solid is filtered in a glassfilter and the weight of the wet filter cake that contains 30-40 wt %water is also determined. This is useful, because the catalyst is usedin this form for catalytic hydrogenation. From the composition of thewet filter cake the amount of the metal used for hydrogenation can beestimated. As the catalyst is non-pyrophoric, it can also be storedunder organic solvents and favourably under alcohol. The metal contentof the dry catalyst is about 20-30 wt %.

The pyrophoric feature was examined as follows:

On each of three pieces of filter paper 1 gram of filter-wet catalystwas piled. The first sample was water-wet, the second one wasimpregnated with ethanol and the third one with methanol. Samples wereplaced into drying owen at 60° C. and kept there until a powder-drystate was achieved. Non of the samples was pyrophoric, what is more, thefilter paper also remained colourless, so it was not even roasted. Thesame results were obtained with catalysts filtered after a hydrogenationreaction in ethanol.

The advantage of the invention is that it provides a simple process forpreparing non-pyrophoric skeleton catalysts. The elimination of thepyrophoric feature and, thereby the reduction of the danger of fire andexplosion means that the most serious disadvantage of skeleton catalystshas been eliminated and by this their scope of application was extended.The support provides a high dispersion to the active metal not obtainedbefore and as a result ensures higher activity. Another advantage isthat the relative density of the catalysts according to the invention isabout 1 (the relative density of the known preparations is about 1.8),so while stirring they distribute in the volume of the reaction mixturemore evenly, additionally they can be filtered out perfectly. Thecatalysts prepared according to the invention are not magnetic unlikethe catalysts made conventionally, therefore, they can be stirred upmore easily. The surface of the catalysts is polar which is favourablein numerous catalytic reactions. As an average the amount of the alkalihydroxide used for the preparation in the present process is one-thirdor even less than the amount used in the known procedures, so theenvironmental pollution is less. Further advantage is that the processis fast and it does not require any special equipment.

The process of the invention is illustrated with the following examples:

EXAMPLE 1

The catalytic hydrogenation activity was measured in a stirred flask, inethanol solution, under one bar pressure, at room temperature, at800-1300 rpm. The reactants were nitrobenzene, eugenol, acetophenone andbenzyl cyanide. The pyrophoric feature of the catalyst was examinedbefore and after the reaction.

70 cm³ of water was put into a 150 cm³ beaker and 10 g of alloy powder(50 wt % Al, 50 wt % Ni, particle size under 60 microns) was added toit. The suspension was stirred and heated to 75° C. To the suspension 20cm³ of 15% alkali solution was dropped while the temperature was 95° C.When the intensity of the foaming decreased significantly 25 cm³ of 25%sodium hydroxide was added to it in one portion and the reaction mixturewas stirred until it cooled down to room temperature. The catalyst wasdecanted and washed to be neutral. The volume of the catalyst was 21 cm³and the weight of the wet filter cake was 20 g. A sample of about 1 gfrom the wet catalyst was placed on a filter paper and impregnated withmethanol and then the preparation was placed into a drying owen anddried at 60° C. In 30 minutes it disintegrated into grey, dry powder andthere was no colour left on the filter paper proving that the catalystis not pyrophoric. The same test was carried out with the catalystfiltered out from the reaction mixture. This sample was not pyrophoriceither.

EXAMPLE 2

70 cm³ of 1% sodium hydroxide and 0.1 g of ammonium chloride were putinto a 150 cm³ beaker. The suspension was stirred and heated at 99-100°C. To the suspension 10 g of alloy powder (50 wt % Ni and 50 wt % Al,particle size under 100 microns) was added. The foaming decreasedsignificantly after 30 minutes, then 6 cm³ 40% of sodium hydroxide wasadded to it. The reaction mixture was kept at 95-99° C. for further 50minutes and then the reaction mixture was decanted and the catalyst waswashed to be neutral. The volume of the catalyst was 40 cm³ and theweight of the wet filter cake was 33 g. The pyrophoric feature wastested as described in the first example. The catalyst was notpyrophoric and magnetic. The catalytic activity was measured in thehydrogenation of benzyl cyanide. The catalyst was active and was notpyrophoric after the reaction either.

EXAMPLE 3

50 cm³ of 1.5% sodium hydroxide was put into a 150 m³ beaker and wasstirred at room temperature. 10 g of alloy powder (50 wt % Al, 50 wt %Ni, particle size under 60 microns) was added to it. The suspension wasstirred for 20 minutes, then it was slowly heated above 92-95° C. andkept at this temperature for further 30 minutes. Then 10 cm³ of 15%sodium hydroxide was added to it. The heating was ceased and thereaction mixture was allowed to cool down to 60° C. The reaction mixturewas decanted and the catalyst washed to be neutral. The volume of thecatalyst was 22 cm³ and the weight of the wet filter cake was 20 g. Thepyrophoric feature was tested as described in the first example. Thecatalyst was not pyrophoric and magnetic. The catalytic activity wasmeasured in the hydrogenation of benzyl cyanide. The catalyst was notpyrophoric after the reaction either.

EXAMPLE 4

250 cm³ of water, 3.75 g of sodium hydroxide and 0.75 g of ammoniumchloride were put into a 800 cm³ beaker and the solution was heatedwhile stirring. To the solution at 60° C. temperature 50 g of alloypowder (47 wt % Al, 53 wt % Ni, particle size under 60 microns) wasadded. The suspension was heated at 99-100° C. until the foamingdecreased (about 20 minutes). Then a solution of 50 cm³ water and 6 gsodium hydroxide having a temperature of 55° C. was added to it. Theheating was ceased and the suspension was stirred until it cooled downto 50° C. The catalyst was decanted and washed to be neutral. The volumeof the catalyst was 106 cm³ and the weight of the wet filter cake was111 g. The pyrophoric feature was tested as described in the firstexample. The catalyst was not pyrophoric and magnetic. The catalyticactivity was measured in the hydrogenation of nitrobenzene andacetophenone. The catalyst was active and not pyrophoric after thereaction either.

EXAMPLE 5

50 cm³ of a solution of 1.5% sodium hydroxide and 0.04 g of lithiumchloride was put into a 150 cm³ beaker. The solution was stirred at roomtemperature and 10 g of alloy powder (50 wt % Al, 50 wt % Ni, particlesize under 60 microns) was added to it. The temperature increased fastup to 95° C. At this point 10 cm³ of 15% sodium hydroxide was added toit in two parts. The reaction mixture was stirred for further 20 minutesat 98-99° C., and then the catalyst was decanted and washed to beneutral. The volume of the catalyst was 26 cm³ and the weight of the wetfilter cake was 26.5 g. The pyrophoric feature was tested as describedin the first example. The catalyst was not pyrophoric and magnetic. Thecatalytic activity was measured in the hydrogenation of benzyl cyanide.The catalyst was not pyrophoric after the reaction either.

EXAMPLE 6

250 cm³ of 1.5% sodium hydroxide and 2.5 g of potassium chloride wereput into a 800 cm³ beaker. The solution was stirred and 50 g of alloypowder (47 wt % Al, 53 wt % Ni, particle size under 60 microns) wasadded to it. The solution was heated at 96-97° C. until the intensivefoaming decreased, then 50 cm³ of 10% sodium hydroxide was added to it.The reaction mixture was heated at 98-99° C. for further 10 minutes thenthe heating was ceased and the suspension was stirred until itstemperature decreased to 50° C. Then the catalyst was decanted andwashed to be neutral. The volume of the catalyst was 100 cm³ and the wetfilter cake was 116 g. The pyrophoric feature was tested as described inthe first example. The catalyst was not pyrophoric and magnetic. Thecatalytic activity was measured in the hydrogenation of nitrobenzene andacetophenon. The catalyst was not pyrophoric after the hydrogenationeither.

EXAMPLE 7

150 cm³ of water, 2 g of sodium hydroxide and 0.38 g of sodium chloridewere put into a 400 cm³ beaker. The solution was stirred and heated to50° C. To the solution 25 g of alloy powder (50 wt % Al, 44.5 wt % Ni,2.5 wt % Mo, 1.5 wt % Co, 1.5 wt % Cr, particle size under 60 microns)was added. The suspension was heated at 95-96° C. and when the foamingwas decreased 35 cm³ aqueous solution of 4 g sodium hydroxide having atemperature of 90° C. was added to it. Then the reaction mixture washeated at 98-100° C. for further 50 minutes. The heating was ceased andthe suspension was stirred until its temperature decreased to 65° C. Thecatalyst was decanted and washed to be neutral. The volume of thecatalyst was 55 cm³ and the weight of the wet filter cake was 50 g. Thepyrophoric feature was tested as described in the first example. Thecatalyst was not pyrophoric and magnetic. The catalytic activity wasmeasured in the hydrogenation nitrobenzene and acetophenon. The catalystwas not pyrophoric after the hydrogenation either.

EXAMPLE 8

150 cm³ of water, 2 g of sodium hydroxide and 0.38 sodium chloride wereput into a 400 cm³ beaker and the solution was stirred. To the solutionat room temperature 25 g of alloy powder (50 wt % Al, 50 wt % Co,particle size under 60 microns) was added. The procedure was furthercarried out as described in example 7. The volume of the catalyst was 38cm³ and the weight of the wet filter cake was 56 g. The catalyst wasmagnetic which indicates that in this way magnetic powder of very finedispersion can be produced. The catalyst was not pyrophoric. Thecatalytic activity was measured in the hydrogenation of benzyl cyanideat 80° C. under 15 bar pressure. The catalyst was not pyrophoric afterthe hydrogenation either.

EXAMPLE 9

A solution was prepared from 60 cm³ of water, 1 g of sodium hydroxideand 0.13 g of ammonium chloride and stirred at room temperature. To thesolution 10 g of alloy powder (29 wt % Al, 70 wt % Si, 1 wt % Pt,particle size under 150 microns) was added. The suspension was heated to90° C., then a solution of 15 cm³ water and 2 g sodium hydroxide wasadded to it in a 10 minute period at 95° C. The reaction mixture washeated for further 30 minutes at 96-98° C. The catalyst was decanted andwashed to be neutral. The catalyst was filtered out and dried at 60° C.14.6 g catalyst was obtained. The volume of the catalyst powder was 32cm³. The pyrophoric feature was tested as described in the firstexample. The catalyst was not pyrophoric. The catalytic activity wasmeasured in the hydrogenation of eugenol. The catalyst was notpyrophoric after the hydrogenation either.

EXAMPLE 10

In a 150 cm³ beaker a solution was prepared from 60 cm³ of water, 1 g ofsodium hydroxide and 0.13 g of ammonium chloride and stirred at roomtemperature. To the solution 10 g of alloy powder (29 wt % Al, 68 wt %Si, 2 wt % Pd, 0.76 wt % Cu, particle size under 60 microns) was added.The temperature raised and reached 92° C. in 10 minutes, then 2 g ofsodium hydroxide in 15 cm³ water was added to the suspension in 7minutes. The reaction mixture was heated for further 15 minutes at92-95° C. The catalyst was decanted and washed to be neutral. Thecatalyst was filtered out and dried at 60° C. The weight of the catalystwas 12.3 g and the volume of the catalyst powder was 24 cm³. Thepyrophoric feature of the catalyst was tested as described in the firstexample. The catalyst was not pyrophoric. The catalytic activity of thecatalyst was measured in the hydrogenation of eugenol. The catalyst wasnot pyrophoric after the hydrogenation either.

EXAMPLE 11

150 cm³ of water, 1.88 g of sodium hydroxide and 0.375 g of ammoniumchloride were put into a 600 cm³ beaker. The solution was heated to 50°C. and 25 g of alloy powder (50 wt % Al, 40 wt % Ni, 3 wt % Cr, 7 wt %Fe, particle size under 100 microns) was added to it. The suspension washeated at 99-100° C. until the foaming was ceased (about 25 minutes),then the heating was stopped and 25 cm³ aqueous solution of 3 g sodiumhydroxide having a temperature of 70° C. was added to it. The suspensionwas stirred until its temperature decreased to 50° C. The catalyst wasdecanted and washed to be neutral. The volume of the catalyst was 53 cm³and the weight of the wet filter cake was 53 g. The pyrophoric featurewas tested as described in the first example. The catalyst was notpyrophoric and magnetic. The catalytic activity was measured in thehydrogenation of nitrobenzene and acetophenone. The catalyst was activein both reactions. The catalyst was not pyrophoric after the reactionseither.

What is claimed is:
 1. A process for the preparation of a supported,non-pyrophoric, skeleton catalyst having a polar surface and comprisingcatalytically active metal(s) in high dispersion by treating an alloypowder of the catalytically active metal(s) and alkali-soluble metal(s)with an aqueous alkali metal hydroxide solution, characterized in thati)first suspending the alloy in a solution having a weight 3-10 times ofthat of the alloy and containing 0.5-4 weight % of an alkali metalhydroxide, where the amount of alkali metal hydroxide in the solutionused is 5 to 30% of the weight of the alloy, or in water and drop-wiseadding a solution containing said amount of alkali hydroxide, ii)subsequently heating the suspension at 90-1000° C. until the intensivehydrogen development stops, iii) subsequently adding to the suspension asolution containing 10-40% alkali hydroxide in such amount that thecontent of the alkali hydroxide relative to the weight of the startingalloy is 10-60 wt %, iv) subsequently stirring the suspension at 30-100°C. for further 3-60 minutes, and v) finally separating and washing toneutral the solid phase containing the active metal(s) and theoxide-hydroxide formed from the alkali-soluble metal(s).
 2. The processof claim 1, wherein the starting alkali hydroxide solution comprises0.5-5 wt %, relative to the weight of the alloy, of ammonium chloride,or sodium chloride, or potassium chloride and/or lithium chloride. 3.The process of claim 2, wherein the catalytically active metal isselected from the group consisting of nickel, cobalt, chromium, copper,manganese, iron, palladium, platinum and mixtures of two or morethereof.
 4. The process of claim 2, wherein the alkali-soluble metal isaluminum, silicon or a mixture thereof.
 5. The process of claim 2,further comprising that the catalyst is stored under a lower alcohol. 6.The process of claim 1, further comprising that the catalyst is storedunder an organic solvent.
 7. The process of claim 1, wherein the one ormore catalytically active metal(s) is or are selected from the groupconsisting of nickel, cobalt, chromium, copper, manganese, iron,palladium, platinum and mixtures of two or more thereof.
 8. The processof claim 1, wherein the alkali-soluble metal is aluminum, silicon or amixture thereof.